Chemical Solidifying And Performance Characterization Of Abandoned Slurry And Soil

Blast furnace slag（BFS）is a by-product of pig iron making,and its amount produced each year is extremely large.In recent years,with the development of modern industry and urbanization in our country,engineering abandoned slurry and soil have become a kind of engineering waste at large scale.Such engineering waste can not be effectively utilized due to its poor engineering performance,and it has gradually become an urgent problem to be solved.This paper aimed to develop out a green cementitious material,named soil stabilizer（SS）,which can turn the abandoned slurry and soil out into engineering materials as it mixing into the later ones and solidifing them.This SS was made by using the BFS powder as main raw material,as soon as using the gypsum,the cement,and other admixture as the activator for the former.In this paper,the following instruments were used to investigate and analyze the solidified specimens of SS for their micro morphology,mechanical properties,and soil solidification mechanisem,respectively.They included the scanning electron microscope（SEM）,the universal testing machine,and other instruments.In the preparation of SS specimens,it was found that the hardened paste specimens of SS had the lower 7d compressive strength（CS）and the obvious increase of 28d CS value as SS composed only by both BFS and gypsum.As the content of gypsum being 20%,the CS value of 28 d was reached 13 MPa for the resulting hardened paste specimen of SS.The softening factors of the resulting hardened paste specimens of SS were increased with the increase of the gypsum content before it being lower than 30%,and then decreased with the increase of the gypsum content after it being higher than 30%.As the gypsum content being30%,the softening factor of the resulting specimens was the maximum value of 0.92.The shrinkage rates were decreases with the increase of gypsum content for the resulting hardened paste specimens of SS.As both the cement and gypsum being used as the activator for BFS to produce the SS specimen,the 7d and 28d CS values of the resulting hardened paste specimens of SS were significantly improved as compared with the specimens composed only by both gypsum and BFS.As the content of cement being 10%,the 28 d CS value of the hardened paste specimens of SS was 29.2 MPa,and the SS was composed by cement,gypsum,and BFS.As the cement content being more than 10%,the CS values of the specimens were decreased with the increase of the content of cement.The softening factors of the resulting specimens were firstly increased with the increase of cement content as it being lower than 10%,and then decreased with the increase of cement content as it being higher than 10%.The softening factor of the resulting specimen was 0.91 as its cement content being 10%.The micro morphology of the resulting hardened paste specimens of SS showed that a large number of needle-like AFT and massive Ca（OH）₂ composed the structure of them.These AFTs were surrounded by the C-S-H gel,and the needle-like AFTs constituted the skeleton of the specimens.The solidified slurry specimens were prepared by incorporating the SS into engineering abandoned slurry.The CS values of 7d and 28d were increased with the increase of the adding amount of SS for the resulting solidified slurry specimens.As the SS content being40%to that of engineering abandoned slurry,the CS value of 28 d was 5.2 MPa for the resulting solidified slurry specimen.The softening factors of the solidified slurry specimens were increased with the increase of the amount of SS,the shrinkage rates of them were decreased with the increase of SS content,and the shrinkage rate of the resulting specimen was 0.92%as the SS content being 20%for it.The solidified soil specimens were prepared by incorporating SS into engineering abandoned soil.The CS values of 7d and 28d were increased with the increase of the adding amount of SS for the resulting solidified soil specimens.As the SS content being 50%to that of engineering abandoned soil,the CS value of 28 d was 18 MPa for the resulting solidified slurry specimen.The softening factors of the solidified soil specimens were increased with the increase of the amount of SS,and the softening facter of the resulting specimen was 0.92as the SS content being 50%for it.The shrinkage rates of them were decreased with the increase of SS content,and the shrinkage rate of the resulting specimen was 0.72%as the SS content being 30%for it.